Mexico City Struggles to Clear the Air Some Pollutant Levels Are Decreasing, but Car and Factory Emissions Still Trouble City

FOR decades the March 18 Oil Refinery in northern Mexico City
belched out enough smoke, gases, and dirt to produce close to 5
percent of the pollution fouling the air of this notoriously
polluted city.

Then in 1991, President Carlos Salinas de Gortari, increasingly
aware of the mounting toll the bad air was taking on residents'
health and the Mexican capital's reputation, announced the refinery
would be closed. Soon, in place of smokestacks, a park, baseball
fields, and an ecological reserve will bloom.

The case of the March 18 Oil Refinery is one small chapter in
the story of Mexico City's recent battle to clean up some of the
worst air-quality conditions in the world. Begun in earnest during
the six-year presidency of Mr. Salinas, who took office in December
1988, the campaign has yielded some important results. It includes
everything from driving restrictions and the world's second-largest
air-quality monitoring system to the planting of millions of trees.

According to an assessment of Mexico City air quality released
last month, average levels of some of the worst airborne poisons,
including lead and carbon monoxide, have been steadily reduced. At
the same time, however, ozone - an eye and throat irritant and
health hazard produced in a photochemical reaction to airborne
hydrocarbons - has tended to stabilize at levels that carry the
designation "poor air quality."

Some public officials are trumpeting the encouraging results.
But even as they do, critics warn that what progress has been made
will be lost if more comprehensive measures aren't taken: notably
to improve traffic flow, to address the city's worsening
public-transit woes, and to get tougher on industrial emissions.

"Mexico City can point to some important successes, but we also
have grave problems to resolve before we can talk about clean
air," says Luis Manuel Guerra, executive director of the National
Autonomous Institute of Ecological Studies (INAINE), a
nongovernmental agency.

Among successful measures, he counts the requirement of
catalytic converters on all cars made after 1991 and the
progressive switch to unleaded gas, which by the end of this year
should account for about half of gas used.

"But with ozone, all we've seen is a stabilization of the
crisis," Mr. Guerra says. "Unfortunately it's stabilization at
very high levels."

Public officials argue that Mexico City should be allowed to
tout its progress. It is the world's most populous megalopolis
(population nearly 20 million) with all the acute economic
challenges of any developing-world city, plus climatic conditions
that exacerbate air-quality problems.

"In five years we've reduced lead levels 90 percent, sulfur
dioxide levels have been within norms equivalent to those of the US
EPA {Environmental Protection Agency} for 31 months running, and
for carbon monoxide it's been 27 months," says Fernando Menendez
Garza, executive director of the Metropolitan Commission for the
Prevention and Control of Mexico Valley Pollution. "I don't know
of any other city whether in the industrialized or developing world
that has controlled to this extent, and in a few years time its
most dangerous pollutants."

Another recent report, based on a five-year joint US-Mexico
study of Mexico City air quality, concluded that reducing certain
contaminants is not enough, since that means remaining pollutants
simply react to each other in different ways often causing new
problems.

Called the Global Air Quality Study and directed by the Mexican
Petroleum Institute, the report acknowledges that the region's
particular natural conditions mean that no one strategy for
combating pollution can be uniformly implemented.

Mexico City is located in a valley surrounded by mountains that
have been denuded of the trees that would act as natural pollution
"processors." The hills trap the pollutants of 2. …

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